[Freeze-etch studies of the chick embryonic skin with special consideration of cell junctions (author's transl)].

The skin of the quail embryo has been investigated microscopically with the help of freeze-etched preparations and the thin section method. On the 11th day of hatching the epidermis consists of the stratum basale and the periderm. They are not keratinized and do not differ concerning their cell junctions. Desmosomes have particles on both fracture faces with a diameter of 8 to 10 nm. Gap junctions consist of particles (5 to 8 nm) on P-face and depressions on E-face. Tight junctions are always small; they consist of spreaded ridges on the cytoplasmic face and grooves on the extracellular face. On the 14th day of hatching the stratum basale is keratinized in part in the outer layers and the periderm has been replaced by the fully keratinized stratum corneum. In the inner layers of the stratum basale cell junctions are identical with the epidermal cells on the 11th day of hatching. In the layers there are additional connexions of desmosomes and keratin fibrils. Tight junctions are absent in the stratum corneum. The size and frequency of gap junctions and desmosomes as well as the number of membrane-associated particles are reduced in comparison to the stratum basale.